The present invention relates to compositions for determination of chloride ion. Determination of chloride ion in body fluids provides useful information regarding abnormal transport, absorption and discharge of various electrolytes, and is clinically significant.
Conventionally, determination of chloride ion in body fluids has been generally conducted by a method wherein chloride ion concentration is determined as electric signals, such as the coulometric titration method using a chloride meter and the electrode method using ion-selective electrodes, or colorimetric determination using mercury thiocyanate and iron nitrate. However, special apparatuses are necessary for the former coulometric titration method and the electrode method, which require care for maintenance and control of the instruments, and pose problems such as inferior sample analysis management efficiency. On the other hand, the latter colorimetric determination generates waste liquor containing cyanogen and mercury after the determination, necessitating special treatment therefor. Alternatively, determination of chloride ion by the enzyme method using nonactivated .alpha.-amylase and reagents for determination of .alpha.-amylase has been adopted recently (Japanese Patent Unexamined Publication No. 126497/1988). In this method, however, a calcium complex is added to a maltooligosaccharide derivative for determination, and poses problems such as prominent rise of reagent blank, poor determination precision, and so on. Also, it has been found that the measurable range is narrower and that dependable measurement values cannot be obtained in the high concentration level which surpasses normal values, posing another problem.